Glacier head

A glacier head is the top of a glacier. Although glaciers seem motionless to the observer they are in constant motion and the terminus is always either advancing or retreating.^[1]

On a glacier, the accumulation zone is the area above the firn line, where snowfall accumulates and exceeds the losses from ablation, (melting, evaporation, and sublimation). The annual equilibrium line separates the accumulation and ablation zone annually. The accumulation zone is also defined as the part of a glacier's surface, usually at higher elevations, on which there is net accumulation of snow, which subsequently turns into firn and then glacier ice. Part of the glacier where snow builds up and turns to ice moves outward from there.

The glacier head is the highest upslope edge of an alpine glacier or the upslope end of the zone of accumulation. The head of the glacier comes up against a steep bedrock cliff called a cirque headwall^[2]